Penicillamine determination using a tyrosinase micro-rotating biosensor

Tyrosinase [EC 1.14.18.1], immobilized on a rotating disk, catalyzed the oxidn. of catechols to o-benzoquinone, whose back electrochem. redn. was detected on glassy carbon electrode surface at -150 mV vs. Ag/AgCl/NaCl 3 M. Thus, when penicillamine (PA) was added to the soln., this thiol-contg. compd. participate in Michael type addn. reactions with o-benzoquinone to form the corresponding thioquinone derivs., decreasing the redn. current obtained proportionally to the increase of its concn. This method could be used for sensitive detn. of PA in drug and human synthetic serum samples. A linear range of 0.02-80 micro M (r = 0.999) was obtained for amperometric detn. of PA in buffered pH 7.0 solns. (0.1 M phosphate buffer). The biosensor has a reasonable reproducibility (R.S.D. <4.0 ) and a very stable amperometric response toward this compd. (more than 1 mo). [on SciFinder (R)]